1. Field of the Invention
The present invention relates to a cable-based sensor, particularly to a cable-based sensor for detecting material level and temperature.
2. Description of the Related Art
For management of bulk material stored in a silo, a sensor for detecting material level is very important. The material level means a height of the material in the silo, and the material level can be converted to obtain the amount of the material stored in the silo. The sensor can be applied to petrochemical industry, food industry, feed industry, steel industry, cement industry, etc. Materials stored in a silo may be solid, liquid, or liquid-solid mixture. For example, the materials may be petroleum, coal, iron sand, cement, flour, cattle fat, etc. When each material is stored in a silo, temperature, moisture and an amount of the material will influence the quality of the materials. In some particular industries, when the temperature of the material stored in the silo is not properly controlled, a dry and dusty material may cause a dust explosion.
When the material is liquid, a conventional sensor can detect temperature, moisture, or material level of the material. The conventional sensor sends magnetic fields produced by voltage-pulses to the material, and detects a feedback of the magnetic fields for calculating the material level. Further, another type of conventional sensor can detect a change between liquid tension of the material and its impedance for calculating the material level.
However, the foregoing conventional sensors cannot detect solid material because detecting cables of the conventional sensors are easily damaged by impacts of the solid material. Therefore, the conventional sensors need to be further improved.